Societies which do not adapt to change risk going into decline and the so-called Maastricht criteria for countries applying for membership of the eurozone are a prime example of rules that badly need changing. They were designed for an EU half the size it is now, with member states with (very) similar income and price levels and rates of economic growth.

The EU of 25 (soon 27) is a very different creature from 15 years ago. There are big disparities in income and price levels. These in turn imply higher economic growth - and inflation - in the new, lower-income, member states.

Where there are floating exchange rate regimes the currency will appreciate, and prices will rise where there are fixed exchange rates. The situation is further complicated by the EU requirement for new member states to 'harmonise', meaning increase, excise duties, which is strongly inflationary.

New member states comply with the criteria either by accepting economic stagnation or by creative accounting and data beautification to manipulate the statistics, the methods favoured in Greece and Italy. Or they can openly disregard the rules, as with Germany and France.

The most sensible solution, evidently, would be to scrap the Maastricht criteria or at least adapt them to the changed circumstances.

The experience of Bulgaria with a currency board, which resembles euro-isation, shows that euro-isation can be beneficial. It imposes fiscal discipline, cuts the budget deficit, and stimulates economic reforms.

The best move for the EU is to follow the 'Big Bang' enlargement with rapid enlargement of the eurozone, which will promote economic stability and reform. All new member states could be offered entry immediately. Where are the negative implications so darkly hinted at by the European Central Bank (ECB)? The combined gross domestic product (GDP) of the new member states is too small a proportion of the Union's GDP to change the monetary conditions. But such a move would be beneficial to new EU member states and relieve them of wearisome smoke-and-mirrors games needed to circumvent the outdated criteria.

If a Big Bang euro policy is not implemented, then the second best option for the new member states is to euro-ise unilaterally, as Lithuania seems to be in the process of doing. Once there is critical mass the Commission and the ECB will simply be forced to recognise the fact.

But recommending a Big Bang policy does not mean that the ECB will necessarily offer the best option for monetary policy in the long run. The ECB is neither accountable nor transparent. It does not even achieve its own goal for inflation - 77% of the time inflation is above target.

So a euro Big Bang policy is no guarantee of success. It requires the ECB's monetary policy strategy to be improved, the introduction of explicit inflation targeting with a symmetric inflation target set by a political authority - for example by Ecofin. And the bank's transparency and democratic accountability urgently need to be strengthened. Without such reforms the euro risks losing its credibility and strength - and many countries might be better advised never to join the eurozone.